Automatic wire gripping terminal



April 21, 1959 v. R. DESPARD 2,883,64L

AUTOMATIC WIRE GRIPPING TERMINAL Filed July 2, 1956 INVENTOR VICTOR R.DESPARD ATTORNEYS United States Patent AUTOMATIC WIRE GRIPPING TERMINALVictor R. Despard, Syracuse, N.Y., assignor to Pass & @zymour, Inc.,Syracuse, N.Y., a corporation of New ork Application July 2, 1956,Serial No. 595,405

8 Claims. (Cl. 339-216) This invention relates to electric wiringdevices and more particularly to automatic conductor gripping terminalsfor use with such devices.

It is a general object of the present invention .to provide a novel andsimple but effective automatic conductor gripping terminal for electricwiring devices.

ing with a single folded wire spring whereby circuits may be easilyforwarded.

Still another important 'object of the invention con- .sists in theprovision of a dual spring wire releasing device of extreme simplicity.

A further important object of the invention consists in the totalabsence of fastening means for the parts of the conductor grippingterminals other than thecover for the general area in which they aremounted.

A'still further object of the invention consists in the arrangement ofthe wire spring releasing means to prevent destructive bending of eitherspring of a dual unit if excess tension is placed on a connectedconductor in an endeavor to withdraw it without releasing the spring.

Other and further objects and features of the invention will be morereadily understood upon a consideration of the accompanying drawing andfollowing specification wherein is disclosed a single exemplaryembodiment of the invention, with the understanding that suchmodifications thereof and substitutions of equivalents may be .madetherein as fall within the scope of the appended claims withoutdeparting from the spirit of the invention.

In said drawings: Fig. 1 is a .rear elevation of a moulded, box-mounting.type of lamp holder fitted with automaticconductor gripping terminalsconstructed in accordance with the present invention;

Fig. 2 is a fragmentary section on :an enlarged scale through the lampholder body and one of the terminals taken on the plane of line 2-2 ofFig. 1;

Fig. 3 is a top plan view of one of the terminals apart from the lampholder base and showing the three parts thereof in assembledrelationship;

.Fig. 4 is a perspective View of the assembled parts of a terminalshowing two conductors gripped thereby;

Fig. 5 is a sectional view similar to Fig. 2 illustrating the manner inwhich the conductor wire gripping is ef- .fected;

Fig. 6 is a view similar to Fig. 5 but showing the wire releasingmechanism in operation; and

lCe

wiring and the wiring devices forming the terminals thereof hasemphasized the need for some means for attaching the wire ends to wiringdevices other than the well known screw type terminals, where the end ofthe wire after being bared of its insulation was formed into an openloop and clamped beneath the head of a binding screw. The time consumedin this operation is considerable, even if all goes well, but if thescrew is inadvertently withdrawn too far and dropped in the litter of anew construction operation, if the proper size screw driver is not athand nor the proper tool for forming the open eye in the end of thewire, then considerable additional time may be expended.

All of the above and other considerations warrant the expenditure of asmall additional percentage in the cost of a wiring device which is morethan recovered in the saving in labor if the wire can be automaticallygripped and connected by the mere operation of poking its bared endthrough a hole or opening in the housing of the Wiring device.

Various forms of automatic wire gripping devices have already appeared,but to some degree they all suffer either from excessive cost ofmanufacture and assembly, in that they necessitate the use of expensivematerials capable of both conducting electricity readily and having goodspring characteristics, or they occupy too much space for some uses.About the only suitable material for the dual purpose of conductivityand springiness is .some form of Phosphor bronze which isrelativelyexpensive compared with other materials used ,in theconstruction of terminal devices.

In accordance with the present invention such costly materials areeliminated by using an open sided, conductorend receiving channel ofconducting material which can be brass, copper or ordinary bronze, inwhich the end of the conductor wire lies, and is held therein andpressed against the bottom of the channel by means of a simple steelwire spring bent into a simple folded shape to be most effective in theperformance of this duty.

The invention is illustrated in connection with a moulded, box-mounting,type of lamp holder, commonly referred to as a box cover socket, butobviously this is merely by way of illustration for the terminal deviceis capable of use in many other positions where suflicient housing depthis available to accommodate it.

Referring now to the drawings, and first to Figs. 1 and 2, it will beseen that the wiring device comprises a moulded, circular base orhousing 10 suitably perforated at 11 and 12 to accept mounting ,orfastening screws which secure it down against a junction or fixture boxof the circular or octagonal type for which it acts as a cover. Thefragmentary section of Fig. 2 illustrates the socket sleeve 13projecting integrally and centrally from the front face of the circularbase shown in 'Fig. 1 and formed of suitable insulation material asporcelain or synthetic resin. The socket sleeve is internally threadedat 14 during the moulding operation to directly accommodate the threadedscrew shell of an incandescent lamp for mechanically positioning in-thesocket. An open channel or groove 15 longitudinally extended through thethreaded portion accommodates a springy contact strap 16 which issufficiently bowed to extend into the socket opening to engage thecrests of the threads on the screw shell of the lamp and make contacttherewith. Obviously there is also acentral lamp contact, not shown, andas illustrated in Fig. 1 the switch mechanism 18, of the pull chaintype, serves to permit control of the flow of current to the lamp asdesired.

Two of the automatic wiring terminals T are shown.- in the largerectangular recess 20' in the back of the device and each is of the dualtype, whereby it may accommodate two conductor ends to facilitatecircuit extension, where desired, without splicing. The recess 20 isonly of slight depth, as shown at 21, Fig. 2, to accommodate "theinsulating closure or cover plate 22, as shown in Fig. 7, which coversup the switch and most of the live portions of the terminals, and has amechanical function as will appear as the description proceeds.

The area 23 at the bottom of the recess 20 is substantially flat and init is the deep, irregularly shaped compartment 24 for receiving theswitch mechanism and the oddly shaped identical chambers 25 of irregulardepth, each for accommodating one of the dual, conductor-wiregrippingterminal devices now to be described.

In Fig. 2 each single wiring terminal is shown to be accommodated in anotch-like chamber or compartment 27, forming an offshoot of chamber 25,as will later appear. Roughly this notch is of V configurationlengthwise as well as transversely, having the straight end wall 30substantially normal to the surface 23 and the bottom wall 31 inclinedto wall 30 at an angle of the order of 50. The wall 31 is also straightexcept for its outer end where it curves upwardly at 32 to meet thesurface 23. The side walls 33 of notch 27 converge toward the bottomwall 31 but adjacent wall 30 are normal to the surface 23.

As seen in Fig. 1 the two walls 30 in each composite chamber 25 arelaterally spaced by a deep vertical passage 34, which in the rightchamber 25, which is depicted in Fig. 2, has an extension 35 in thenature of an opening from chamber 25 into the interior of socket 14, andin this is an extension of the screw shell engaging contact 16 which isintegral with and extends centrally from the bottom of a terminal plate37, which is common to both wire grippers in a chamber 25. In the otherchamber 25 a short extension from plate 37 is riveted as shown at 37 toa switch contact.

Each terminal plate 37 has a fiat central section 38 bordered by bent ortrough-like portions 39 forming grooves 40, one at either longitudinaledge thereof. The material of these grooves is first bent substantiallyat right angles to the plane of the flat portion 38, then bent in anarc, to a radius slightly larger than that of the largest conductor tobe connected thereto, until it extends parallel to the first bentportion, and is then extended some distance beyond the inner face of thearea 38, as shown at 41. At either side of the extension tang 36, andits equivalent on the other terminal plate, the lower plate edge isstraight, as shown at 44 in Fig. 4, to rest against the wall 45 at thebottom of notch 27 adjacent flat wall 30, thus positioning the terminalplate against further movement into the compartment. The upper edge 46of the terminal plate is also straight and arranged flush with thesurface 23 to be engaged by the cover plate and prevented fromlongitudinal movement out of its chamber.

Projecting beyond the edge portion 46 of the terminal plate are theextensions 47 of grooves 39, but of considerably lesser depth, as seenat 48, Fig. 2. These are intended to project into and be flush with theouter face of the wire entrance holes 50 in cover plate 22, where theyinsure accurate alignment of these holes with the grooves, and presenteasy entrance apertures for longitudinally inserting the conductorwires.

Each compartment 27 of chamber 25 has sloping side walls 33 mergingtoward the bottom, as seen in Fig. l, and, where they meet the inclinedbottom Wall 31, the width is substantially that of the wire 52 fromwhich the conductor wire gripper springs are formed. This is a harddrawn steel wire in the nature of piano wire having extreme resilience.For each dual gripper device a single piece of this wire is used, bentinto the form of dual grippers, as best seen in Figs. 1, 2 and 4. Suchdual grippers include the common central cross bar 53, the right angledextensions 54 therefrom and lying in the same plane, and the straightterminal portions 56 each connected to an extension 54 by a short radiusare 55. The length of extensions 54 is such as to reach in Fig. 2 fromthe bottom wall 45, in the area accommodating the terminal plate, tosubstantially the curve 32. The free ends 57 of the terminal portions ofthe springs substantially engage the material of the terminal plate eachat the bottom of its respective channel, as best seen in Figs. 2 and 4.

The construction of the gripper spring unit is such that it may bedropped in position in chamber 25 and its extensions, following thepositioning of the terminal plate therein and will automatically assumethe arrangement shown in Figs. 1 and 2, with the cross bar 53 resting at57 against the inner flat face of the terminal plate and the extensions54 resting on the notch bottoms 31 with their curved elbow portions 55just clearing the curve at 32. The portions 58 of the arcs 55 are justbeneath the level of the surface 23.

The arms 56 form an angle of substantially included between them and theline of the bottom of the channel, this smaller included angle beingpresented outwardly so that as a bared wire conductor is pressed downinto the channel from hole 50 it will engage near the free end of arm 56and press it downwardly to the position shown, for instance, in Fig. 5,separating its tip sufliciently from the bottom wall of the channel toadmit the wire at this end. Under these circumstances the spring arm 56returns as far as it can, engages the conductor wire and forces ittightly against the wall of the channel bottom. The angular relationshipis such that the conductor wire cannot be withdrawn, for on effort topull it out the arm 56 is only lifted and more tightly presses its freeend thereof against the conductor wire and the latter against thechannel wall. The ends of arms 56 are cut oif cleanly at right angles topresent a biting edge. The whole spring assembly is prevented frommoving backwardly and hence releasing the conductor by engaging againstthe faces 32 at the back end of each of the portions 27 of the terminalrecess. The cover 22 engages the spring at the points 58 should itattempt to move upwardly and prevents withdrawal and hence conductorrelease.

Release may be effected, however, of one or both conductor wires, in oneterminal, simultaneously by means of a device now about to be described.This comprises a plate of relatively thick metal 60 of a width to justfit between the extended wings 41 of the channel edges, as seen in Fig.3, with one of its faces resting against the surface 38 of the terminalplate. The opposite face of the release plate 60 bears against thesurface 62 of the portion of the base forming the separator between thenotches 27 of the terminal recess. This wall 62 stops at the heightindicated by the reference character 63, Fig. 2, for a purpose later tobe described. At 65, a distance below the upper face of the plate 60determined by the positions of the spring arms 56, the plate is narrowedby cutting away the portions numbered 64 in Fig. 4, whereby a tongue 66is formed which passes between the arms 56 while the surfaces 65 rest onthem. The lower end of the tongue stops short of the cross bar 53located at 57 in Fig. 2.

It will be seen that if pressure is applied downwardly on the topsurface of release plate 60, the surfaces 65 will press down on the arms56 and flex them out of contact with conductors, as in Fig. 6, which maybe in the grooves, so that these may then be withdrawn readily.

The top surface of the release plate is normally held flush with thesurface 23, as seen in Fig. 2, by the arms 56, but is prevented frommoving upwardly from this position by engagement with the cover plate.This arrangement prevents destructive bending of any of the spring arms56 by excessive withdrawal tension on any conductor held thereby. Byproperly adjusting the height of the wing portions of the release plateswhich overlie 5 the spring arms 56, the ends of the latter may beprevented from approaching any closer to the bottoms of their channelsthan desired and thus conductor wire cutofi on excessive withdrawaltension be prevented.

In order to permit access to the release plates, the cover plate aboveeach of them is provided with an elongated slot 68 therethrough, onearranged between each pair of channel entrance holes 50, and having itslong dimensions transverse to an axis connecting the pair of holes. Thusa screw driver with a relatively small blade may be pressed through theslot 68 and engage transversely across the upper edge of the releaseplate for pushing the latter downwardly for releasing conductors. Thisexplains the cut-away area above the surface 63 on the centralpartition, for that provides room for inward movement of the screwdriver blade. In order that the blade may also be not interfered with bythe upper edge of the channeled terminal plate, this is provided with acentral slot 70, clearly seen in Figs. 1, 3 and 4. To prevent excessiverelease movement which might damage the dual grippers, the screw driverblade is stopped by surface 63 and by the bottom of slot 70 to limit itspenetration. Moreover the tongue 66 of the release blade bottoms oncross wire 57 as seen at Figure 6.

The device described is highly effective for holding conductor wires,permits them to be inserted by mere pushing, permits their release withthe use of a tool common with all electricians, and provides aconstruction extremely simple and effective. No complicated parts areinvolved and none are fastened in position other than by the cover platewhich receives fastening screws through the openings 75 and into theholes 76 in the material of the base. The assembly is extremely simpleand cannot go wrong. The springs, which are of steel, do not conduct anycurrent and hence their temper cannot be drawn.

I claim:

1. In a wiring device housing containing at least one contact member andmeans for automatically gripping and connecting a pair of conductorwires to said contact comprising a terminal plate electrically connectedto said contact and having two parallel grooves therein with one end ofeach extending and exposed through a wall of said housing to slidablyreceive an end section of one of said conductor wires therein, aconductor wire gripping means for each groove comprising two straightarms of spring wire having an integral connecting elbow and divergingtherefrom at an included angle of the order of 35, a recess in saidhousing having a wall supporting and positioning said terminal plate andpairs of converging walls forming narrow channels for said grippingmeans with one of the arms of each gripping means being the grippingarms and inclined at an angle of the order of 85 to the bottom of saidgroove and having its free end substantially in engagement with saidbottom for directly gripping said wire, the junctions of the convergingwalls of each recess channel supporting the other arm of each grippingmeans substantially throughout its length at an angle of substantially50 to said groove bottom and out of contact therewith, means connectingthe other arms of said gripping means together at their remote endswhereby the pairs of divergent arms are selfmaintained in parallelplanes, said connecting means engaging against said terminal platebetween the said grooves, and a removable cover for said recess adaptedto engage said elbows to maintain said gripping means in said recess.

2. The device of claim 1 in which the terminal plate has an intermediateraised flat portion between said spaced, parallel grooves, and a singleconductive release device slidable over said fiat portion and engagingsaid gripping arms of said two gripping means for flexing themsimultaneously out of contact with the groove bottoms.

3. An automatic conductor wire gripping terminal comprising aninsulating base having a substantially fiat outer surface, dual,parallel, laterally spaced V-notches in said base terminating at theirlarger ends at said surface and with one wall common to each V extendingto meet the other and being substantially normal to said surface, aterminal plate, having grooves formed along spaced parallel edgesthereof, in said notches with the convex sides of said grooves againstsaid common wall, a wire gripping means comprising straight, divergentarms of spring wire integrated by a sharp bend and arranged in each saidnotch with the free end of each outermost arm substantially engaging inthe bottom of one of said grooves at a lower position below said outersurface than the bend between the arms of a pair, means connecting theinner ends of the other arms together and bearing on said terminal platebetween said grooves, and a flat cover sheet for said notches bearing onsaid surface, having a conductor wire entrance opening in line with eachsaid groove, and serving to retain said wire gripping means in saidnotches by engagement with said bends.

4. The device of claim 3 in which said terminal plate has a raised areabetween said grooves, a wall of said base being spaced from and parallelto said area, a release plate slidable between said area and lastmentioned wall and having arms extending over and resting on theoutermost arms of said gripping means, and an opening in said cover forthe insertion of a tool for pressing said release plate down to flex thegripping arms away from the groove bottoms to release conductor wiresgripped thereby.

5. The device of claim 4 in which the last mentioned cover opening iselongated to accept the blade of a screw driver and extends between theconductor wire entrance openings and transverse through an axisconnecting them.

6. The device of claim 5 in which said terminal plate is notched in theupper edge of said raised area to clear a screw driver blade used todepress said releasable plate.

7. The device of claim 4 in which the outer groove walls extend beyondthe plane of said raised area on the terminal plate in the direction ofand to provide end guides for the release plate.

8. The device of claim 4 in which said release plate slides in a planenormal to the said cover, said plate being sized to engage the undersideof said cover to limit the approach of the outermost arms of the wiregripping means to the bottoms of the respective grooves to preventconductor wire cut-off on excessive withdrawal effort thereon.

References Cited in the file of this patent UNITED STATES PATENTS2,705,785 Benander Apr. 5, 1955 2,705,787 Benander Apr. 5, 19552,738,482 Benander Mar. 13, 1956

